The word “printer” as used herein encompasses any apparatus, such as a digital copier, book marking machine, facsimile machine, multi-function machine, etc., that produces an image with a colorant on recording media for any purpose. Continuous feed printers produce images on a continuous web of recording media which passes by the marking engine. Continuous feed printers also include heaters to warm the web of recording media and/or the ink which produces the images at various stages during the printing process.
By way of example, FIG. 10 depicts a prior art continuous web inkjet printer 800. In the embodiment shown, the printer 800 implements a process for printing onto a continuous media web. The continuous web printer system 800 includes twenty print modules 880-899, a controller 828, a memory 829, guide rollers 816, pre-heater roller 818, apex roller 820, leveler roller 822, tension sensors 852A-852B, 854A-854B, and 856A-856B, and velocity sensors, such as encoders 860, 862, and 864. The print modules 880-899 are positioned sequentially along a media path P and form a print zone from a first print module 880 to a last print module 899 for forming images on a print medium 814 as the print medium 814 travels past the print modules. Each print module 880-883 provides a magenta ink. Each print module 884-887 provides cyan ink. Each print module 888-891 provides yellow ink. Each print module 892-895 provides black ink. Each print module 896-899 provides a clear ink as a finish coat. In all other respects, the print modules 880-899 are substantially identical. The media web travels through the media path P guided by rollers 816, pre-heater roller 818, apex roller 820, and leveler roller 822. A heated plate 819 is provided along the path. The pre-heater roller 818, apex roller 820, and leveler roller 822 are each examples of a capstan roller that engages the media web 814 on a portion of its surface. A brush cleaner 824 and a contact roller 826 are located at one end 834 of the media path P. A heater 830 and a spreader 832 are located at the opposite end 836 of the media path P.
Operation and control of the various subsystems, components and functions of printing system 800 are performed with the aid of a controller 828 and memory 829. In particular, controller 828 monitors the velocity and tension of the media web 814 and determines timing of ink drop ejection from the print modules 880-899. The controller 828 can be implemented with general or specialized programmable processors that execute programmed instructions. Controller 828 is operatively connected to memory 829 to enable the controller 828 to read instructions and to read and write data required to perform the programmed functions in memory 829. Memory 829 can also hold one or more values that identify tension levels for operating the printing system with at least one type of print medium used for the media web 814. These components can be provided on a printed circuit card or provided as a circuit in an application specific integrated circuit (ASIC). Each of the circuits can be implemented with a separate processor or multiple circuits can be implemented on the same processor. Alternatively, the circuits can be implemented with discrete components or circuits provided in VLSI circuits. Also, the circuits described herein can be implemented with a combination of processors, ASICs, discrete components, or VLSI circuits.
As illustrated in FIG. 10, the media web 814 passes various heating elements such as, for example, the heated plate 819 and the heater 830, each of which applies heat to the media web to facilitate subsequent processing. Other embodiments of continuous web printers may include other heating elements positioned in varying locations along the media path P. At each location along the continuous web printer system 800 where a heating element applies heat to the media web 814, a risk exists that the media web can be weakened by the heat and break. One previous attempt to prevent printer heating elements from degrading media includes placing a metal screen between the heating element and the media. The screen absorbs heat, however, and if the media contacts the metal screen, the screen can overheat the media. Accordingly, in printers that include heating elements positioned along a media path, reliably preventing the heating element from degrading the media web 814 is a desirable goal.